1. Field of the Invention
The present invention relates to an automatic tension spring mounting device for automatically mounting tension springs which are used to suspend a pad receive member on a seat frame in a vehicle seat or the like.
2. Description of the Prior Art
In a seat for use in a vehicle or the like, there is employed a cushion structure. A typical example of such cushion structure is disclosed in Japanese Utility Model Publication No. 5882 of 1972.
Specifically, in the above disclosed cushion structure, as shown in FIG. 1, between front and rear frames (1a), (1b) of a seat frame (1) located within a seat, there are provided a plurality of wires (3) so as to extend between two side members (2a), (2b), and a separation member (4) is inserted between the wires (3) to thereby provide a so-called screen-like pad receive member (5); and, the thus constructed pad receive member (5) is resiliently mounted at the two sides thereof by means of a plurality of tension springs S, so that a comfortable cushion effect can be obtained by the resiliency of the tension springs S.
In mounting the tension springs S for the pad receive member (5) in the seat frame (1), one of two hooks respectively provided symmetrically in the two ends of each of the tension springs S is hitchingly secured to a side member of the pad receive member (5), and the other hook is inserted into an engagement bore (6) formed in the seat frame (1) as the engagement portion thereof. That is, first, in this manner, a required number of the tension springs S are sequentially mounted from one side to one of front and rear portions of the seat frame (1), and after than a required number of tension springs are mounted similarly to the other portion of the seat frame (1).
However, since the above-mentioned operation to mount the tension springs requires a very large amount of labor and is thus not efficient, there has been recently proposed an automatic tension spring mounting device which is arranged such that a plurality of tension springs can be mounted simultaneously by use of an industrial robot.
However, in such simultaneous mounting of a plurality of tension springs using the industrial robot, it is difficult to insert all of the hooks of the tension springs into the engagement bores in the seat frame such that the hooks can accurately correspond to the engagement bores respectively. In order to cope with this problem, each of the engagement bores must be formed so as to have a sufficient diameter, the engagement bores must be located at equal intervals, angles of assembly of the tension springs must be set as parallel to one another, and dimensional errors in the seat frame and in the tension springs must be eliminated almost completely. However, it is found impossible, as a matter of fact, to meet all of these requirements, because the above-mentioned device must be changed to design and the processing costs thereof must be increased so as to satisfy the requirements.